Gas-Particle Flow Within a High Temperature Solar Cavity Receiver Including Radiation Heat Transfer

1987 ◽  
Vol 109 (2) ◽  
pp. 134-142 ◽  
Author(s):  
G. Evans ◽  
W. Houf ◽  
R. Greif ◽  
C. Crowe
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Particle Interaction ◽  
Computer Code ◽  
Solid Particles ◽  
Forced Flow ◽  
Discrete Ordinates ◽  
Temperature Profiles ◽  
Thermal Coupling ◽  
Solar Receiver

A study has been made of the flow of air and particles and the heat transfer inside a solar heated, open cavity containing a falling cloud of 100-1000 micron solid particles. Two-way momentum and thermal coupling between the particles and the air are included in the analysis along with the effects of radiative transport within the particle cloud, among the cavity surfaces, and between the cloud and the surfaces. The flow field is assumed to be two-dimensional with steady mean quantities. The PSI-Cell (particle source in cell) computer code is used to describe the gas-particle interaction. The method of discrete ordinates is used to obtain the radiative transfer within the cloud. The results include the velocity and temperature profiles of the particles and the air. In addition, the thermal performance of the solid particle solar receiver has been determined as a function of particle size, mass flow rate, and infrared scattering albedo. A forced flow, applied across the cavity aperture, has also been investigated as a means of decreasing convective heat loss from the cavity.

Numerical Analysis of Crust Behavior of Molten Core and Concrete Interaction by Using MPS Method

2014 ◽  
Author(s):  
Takeo Watanabe ◽  
Yoshiaki Oka
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Particle Interaction ◽  
Nucleate Boiling ◽  
Phase Changes ◽  
Solid Particles ◽  
Experimental Result ◽  
Conductive Heat ◽  
Radiation Heat ◽  
Mps Method

Moving particle semi-implicit (MPS) method is the particle (girdles) method for incompressible medium. Particles are used for discretization of fluids, and governing equations are transformed to particle interaction models. Phase changes are treated as changing particle dynamics. The interface is treated accurately. In the present study, two-dimensional code is created for molten core concrete interaction (MCCI) by using MPS method. Each particle has enthalpy, and three types of heat transfer are treated. Conductive heat transfer is calculated with Laplacian model of MPS. Nucleate boiling and radiation heat transfer is calculated by removing enthalpy from surface particles. Liquid particles can be changed to solid particles depending on their enthalpy. These particles are fixed to space. Semi-implicit method is used in original MPS method, but in this study, explicit method is introduced in order to increase calculation speed. The SWISS-1 and SWISS-2 experiments are analyzed. Gas release from concrete is ignored, and melting of concrete is treated as disappearing of particles. This generate void between crust bridge and liquid debris in SWISS-2, and crust bridge is heated mainly by radiation heat transfer. Calculated ablation rate of concrete agrees well with experimental results of SWISS-1 and SWISS-2, but calculated heat flux from crust bridge to the water pool of SWISS-2 is lower. It is because the water penetration through the crust is ignored, and the amount of penetrated water is estimated by the difference between calculation and experimental result.

Radiative Heat Transfer During Growth of Carbon Nanotubes by Vertical Electric-Arc Process

2005 ◽  
Author(s):  
A. G. Ostrogorsky ◽  
L. R. Glicksman
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Optical Thickness ◽  
Radiation Heat Transfer ◽  
Small Diameter ◽  
Side Surface ◽  
Cathode Side ◽  
Discrete Ordinates ◽  
Limited Data ◽  
Electric Arc Process

A macroscopic finite elements model of heat transfer occurring during production of carbon nanotubes was developed. Radiation heat transfer was modeled using the Discrete Ordinates (DO) model and the Rosseland diffusion approximation. The arc is modeled as semitransparent, with the optical thickness ranging from zero to infinity. The results are compared to the limited data available. The optical thickens has a significant impact on the temperature field in (i) the arc and (ii) the anode surfaces exposed to the arc. The temperature of the cathode side-surface on which the small diameter carbon nanotube grew, is not sensitive to the optical thickness of the arc. The model indicates that the optical thickness of the arc should be high, aL ≥ 100.

Radiation Heat Transfer in Fluidized Beds: A Comparison of Exact and Simplified Approaches

1994 ◽  
Vol 116 (3) ◽  
pp. 652-659 ◽  
Author(s):  
G. Flamant ◽  
J. D. Lu ◽  
B. Variot
Keyword(s):  
Heat Transfer ◽  
Fluidized Beds ◽  
Radiation Heat Transfer ◽  
Discrete Ordinates ◽  
Transfer Model ◽  
Radiation Heat ◽  
Flux Divergence ◽  
Transfer Coefficients ◽  
Variable Porosity ◽  
Radiation Exchange

Radiation heat transfer at heat exchanger walls in fluidized beds has never been examined through a complete formulation of the problem. In this paper a wall-to-bed heat transfer model is proposed to account for particle convection, gas convection, and radiation exchange in a variable porosity medium. Momentum, energy, and intensity equations are solved in order to determine the velocity, temperature, radiative heat flux profiles and heat transfer coefficients. The discrete-ordinates method is used to compute the radiative intensity equation and the radiative flux divergence in the energy equation. Both the gray and the non-gray assumptions are considered, as well as dependent and independent scattering. The exact solution obtained is compared with several simplified approaches. Large differences are shown for small particles at high temperature but the simplified solutions are valid for large particle beds. The dependency of radiative contribution on controlling parameters is discussed.

Validation of the Isis-3D Computer Code for Simulating Large Pool Fires Under a Variety of Wind Conditions

2003 ◽  
Author(s):  
Miles Greiner ◽  
Ahti Sou-Anttila
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Temperature Response ◽  
Diffuse Radiation ◽  
Computer Code ◽  
Time Dependent ◽  
Fuel Vapor ◽  
View Factor ◽  
Pool Fires ◽  
Fuel Evaporation

The Isis-3D computational fluid dynamics/radiation heat transfer code was developed to simulate heat transfer from large fires. It models liquid fuel evaporation, fuel vapor and oxygen transport, chemical reaction and heat release, soot and intermediate species formation/destruction, diffuse radiation within the fire, and view factor radiation from the fire edge to nearby objects and the surroundings. Reaction rate and soot radiation parameters in Isis-3D have been selected based on experimental data. One-dimensional transient conduction modules calculate the response of simple objects engulfed in and near the flames. In this work, Isis-3D calculations were performed to simulate the conditions of three experiments that measured the temperature response of a 4.66-m-diameter culvert pipe located at the leeward edge of 18.9-m and 9.45-m diameter pool fires in crosswinds with average speeds of 2.0, 4.6 and 9.5 m/s. The measured wind conditions were used to formulate time-dependent velocity boundary conditions for a rectangular Isis-3D domain with 16,500 nodes. Isis-3D accurately calculated characteristics of the time-dependent temperature distributions in all three experiments. Accelerated simulations were also performed in which the pipe specific heat was reduced compared to the measured value by a factor of four. This artificially increased the speed at which the pipe temperature rose and allowed the simulated fire duration to be reduced by a factor of four. A 700 sec fire with moderately unsteady wind conditions was accurately simulated in 10 hours on a 2.4 GHz LINUX workstation with 0.5 GB of RAM.

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